Analysis of Climate Change Impact on U.S. Crop Yields with Reanalysis Data

Abstract:

Increasing the world population, food security in the sense of supplying enough food has become more important. Cereals are considerable matter in food security issues, and production of cereals are heavily threatened by climate change. In 2012, terrible drought which might happen once in a hundred years, caused massive damage to the soybean and corn harvest. This event had impact on the agriculture industry in U.S., and led drastic increase of commodity price. To ensuring food security, influence of climate risk to food production should be comprehended quantitatively.
We used ERA-Interim which includes temperature, dew-point, pressure, precipitation, solar radiation and wind speed product, to analyze the world condition of climate changes, and calculated warmth index and dew-point depression. Kira (1977) developed warmth index which has close relationship between distribution of plants living. Dew-point depression represents the wetness of atmosphere. Also, we analyzed crop yields statistics from USDA to clarify what kind of climate condition affect crop yields.
Figure 1 shows variance distribution of warmth index. It can be said that area where contains high value of variance, is subject to extreme climatic changes. Figure 2 is a distribution map indicating whether warmth index was higher or lower than average value. In 2012, it was very hot in the wide range of the Russia and North America.
Figure 3 shows correlation between yield index and ERA-Interim climate data at each month. Crop yields have been in trend of increasing because technology enhancements such as improving of breeds and cultivation have been occurred. Therefore, we calculated simple moving average as normal value and calculated yield index by dividing the normal value and annual yields (left Figure 3). If yield index was under 100, it was harvest failure in that year. In contrast, if yield index was higher than 100, it was good harvest in that year. In this result, temperature, warmth index and dew-point depression had nearly 0.7 negative correlation coefficient between yield index during July and August. Also, precipitation had nearly 0.5 correlation coefficient during July. Thus, corn yields were strongly affected by the high temperature or condition of vapor in the atmosphere during the summer season.